The invention relates to improvements in machines for treating elongated flexible bodies, such as webs or strips of metallic, plastic, textile or other material which are to be subjected to one or more treatments, e.g., drying, wetting, cooling, heating, coating, stretching, dipping and/or others. More particularly, the invention relates to improvements in apparatus which can be used in such machines to thread the leaders of elongated flexible bodies into an elongated path along which the bodies must be transported (e.g., pushed and/or pulled) in the course of treatment at one or more stations.
It is already known to employ automatic threading apparatus for the leaders of webs or strips of flexible material (e.g., paper) which must be advanced along an elongated and often quite complex path (e.g., along a path having straight and slightly and/or strongly curved sections). For example, British Pat. No. 1 240 790 discloses a threading apparatus wherein an endless chain conveyor is adjacent the path for the elongated flexible body to be treated in a processing machine. The chain conveyor carries a gripper (such as tongs) which can engage the leader of the flexible body and entrains the body along the prescribed path when the conveyor is set in motion. A similar threading apparatus is disclosed in British Pat. No. 2 133 77 wherein the conveyor is an endless chain or an endless toothed belt and is provided with an entraining element in the form of a pin or clamp which can be caused to engage the leader of the flexible body. A drawback of the above described and other conventional threading apparatus (e.g., those wherein the nips of advancing rolls must be opened by chain or belt followers in order to provide room for introduction of the leader of an elongated web or strip of flexible material) is their complexity, bulk and high cost. Furthermore a chain conveyor is likely to generate much noise and requires constant or frequent lubrication and/or other forms of maintenance.